1. Field of the Invention
The present invention relates to a high nitrogen flux cored wire for all position welding of Cr--Ni type stainless steel, which is used for welding of Cr--Ni type stainless steel, superior in corrosion resistance of welded metal and can improve workability in welding at all position.
2. Description of the Related Art
Stainless steel having high nitrogen content, such as SUS304N2 and SUS329J3L and so forth, has high corrosion resistance and high strength. Therefore, it has been widely applied as strength member in construction, structural member of various tanks, water gates and so forth.
In welding of these members, a welding material which has similar composition to a base material is basically and frequently used. A large number of kinds of steels of wires are present similarly to the base metal. On the other hand, as welding method of these, various methods have been applied. Particularly, welding by means of flux cored wire has been widely employed.
In the recent years, concerning the flux cored wire for welding of high nitrogen Cr--Ni type stainless steel applied for welding of the base metal of high nitrogen content, improvement of workability in welding has been demanded similarly to the flux cored wire with low nitrogen content particularly, when there is a constraint in configuration of the member, jig or so forth or when a structural member is to be constructed by welding, good workability in vertical position welding and overhead position welding becomes necessary because all position welding is required for welding of those members. Namely, in concrete, development of flux cored wire achieving superior arc stability, slag removing characteristics, bead shape and slag coverage, has been highly desired.
Therefore, high nitrogen flux cored wire for welding of stainless steel which can improve welding workability in vertical position welding by restricting content of specific compound in the flux at an appropriate amount, has been proposed (Japanese Unexamined Patent Publication (Kokai) No. Heisei 3 (1991)-264194).
However, when nitrogen content in the wire becomes high, slag removing characteristics can be lowered and the bead shape in the overhead position welding may be degraded. On the other hand, a welding current applicable for the vertical position welding is limited in the extent of 120A to make allowable welding condition quite narrow. Therefore, when welding is performed for construction, in practice, application of the wire is limited and skillful welding becomes necessary. Accordingly, development of high nitrogen stainless steel flux cored wire for all position welding, which can widen applicable range of current, achieve good workability, and improve working efficiency has been strongly demanded.
On the other hand, a flux cored wire for welding of Cr type stainless achieving good welding workability and improvement in anti-cracking property and toughness, has been proposed (Japanese Unexamined Patent Publication No. Heisei 3(1991)-42195. However, in such wire, the nitrogen content in the wire is in the range of 0.02 to 0.06 wt %, and thus is not applicable for welding of high nitrogen Cr--Ni type stainless steel.